Java's OOAD

1.UML

A. Full name: Unified Modeling Language

B.UML diagram: Flowchart, use case diagram, time series diagram, class diagram

C. Between the interface and the class--implementation

D. Between objects and objects

① generalization--is not called inheritance in UML, but is called generalization

② Association

Dependency: Use A is a weakly associative relationship

Aggregation: Has a whole and part of the relationship, but separable

Combination: Contains a whole and part of the relationship, but cannot be separated (also known as strong aggregation)

Note: In Java, aggregation and composition are basically the same, and there's no big difference

2. Design principles

A. Standards for measuring the quality of software design: readability, reusability, scalability, maintainability

B. Standard summary: cohesion, low coupling

C. Seven major principles:

① Single Duty principle: A class should have only one cause for his change

② Opening and closing principle: open to expansion, closed for modification (core principle)

③ Richter Substitution principle: After a subclass replaces all the parent classes, it works as expected

④ relies on the reverse principle: high-level modules should not rely on low-layer modules, they should rely on abstraction

Abstractions should not be dependent on detail, and detail should be dependent on abstraction

⑤ interface Isolation principle: Minimum Interface principle

⑥ combination/Aggregation multiplexing principle: Multi-use combination/aggregation, less inheritance

⑦ Dimitri Law: the principle of least knowledge

Java's OOAD